Puuvillapohjaisen selluloosakarbamaatin elinkaaritase
Abstract Fashion industry is launching new trends in accelerating speed and that leads to increasing amount of discarded textiles. At the same time, there is need for new raw materials and that is why using discarded textiles in fibre manufacturing is important area of research. In an ideal scenario, textile industry would gain a closed loop economy by efficient sorting and material processing back to textile fibre. Benefits of recycling also include that discarded textiles don´t need cultivation like virgin materials, such as cotton. Cotton needs large amounts of water and chemicals to grow and because of this the environment gets strained. In this research, discarded cotton textile is used to produce new regenerated textile fibre called cellulose carbamate (CCA) fibre. The process is based on derivatisation of cellulose with urea to form cellulose carbamate. Environmental impacts for 12 CCA factory models are evaluated through life cycle inventory (LCI) and global warming potential (GWP). Variables are made for three processes where one (CCA 1) is representing a new factory where materia is added to the process the first time. Second process (CCA 2) is based on CCA 1 but it has a circulation for chemicals and water. Only input needed in CCA 2 is materia that evaporates or turns in to salt. In the third process (CCA 3), chemicals and water are recycled but the need for NaOH and H2SO4 is 80 % less than those in CCA 2 because of electrodialysis that consumes electricity 600 % times more than CCA 2. These three processes are simulated as integrated and stand alone factories in location A and B. Results are compared with references cotton and viscose. The LCIs were calculated with VTT´s SULCA 5.0 software, GWP was determined with the ReCiPe Midpoint H life cycle impact assessment (LCIA) method and allocation was done by cut-off-method. The scope of this research starts at the sorting facility and ends with 1000 kg of baled CCA fibre. As a result, the integrated CCA 3 process has 20 % smaller GWP value than CCA 2 and 60 % smaller than CCA 1 despite increased electricity consumption. The GWP reduction potential of factory integration is 25 % with CCA 1, 40 % with CCA 2 and 45 % with CCA 3. The integrated CCA 3 process has 35 % lower GWP value and 98 % lower water consumption than the reference cotton. Compared to Lenzing viscose Asia, the integrated CCA 3 has 66 % lower GWP and 90 % lower water consumption. Integrated Lenzing viscose Austria has 7 % smaller GWP than the integrated CCA 3, but CCA 3 has 93 % lower water consumption. Where CCA uses urea in the derivatisation of cellulose viscose process uses carbon disulphide that is highly toxic. As a conclusion most promising ways to decrease the GWP of the CCA process is its integration to a pulp mill and by decreasing the amount of process chemicals through efficient circulation or through electrodialysis. ...
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